Thermoplastic vulcanizates are well known in the art. They offer a substantial economic advantage because they have many of the properties of an elastomer, but yet are processable as thermoplastics.
Nitrile rubber, which is oil resistant, has advantageously been used as the elastomer of choice in thermoplastic vulcanizate products that are useful in oil rich environments, such as many automotive products. For example, U.S. Pat. No. 4,104,210 teaches thermoplastic vulcanizates including high unsaturation diene rubber particles, e.g., nitrile rubber particles, dispersed throughout a crystalline thermoplastic polyolefin resin, e.g. polyethylene.
Likewise U.S. Pat. No. 4,355,139 teaches compatibilized blends of nitrile rubber, thermoplastic olefin polymers, and a compatibilizing amount of a copolymer comprising at least one molecular segment each of nitrile rubber and olefin polymer. Upon dynamic vulcanization, compositions comprising fifty parts or more of cured nitrile rubber per one hundred parts by weight of olefin polymer are elastomeric. These compositions are fairly resistant to swelling in hot oil.
Besides being resistant to swelling in hot oil, many applications for elastomeric articles also require that the elastomeric compositions from which they are made are less oil permeable. In other words, although some elastomeric compositions are oil resistant, they may allow for the passage of oil therethrough.
Accordingly, there is a need in the art to develop elastomeric materials, preferably thermoplastic vulcanizates, that are resistant to oil, and have improved resistance to hot oil transport therethrough.